I discovered that the problem is not in the rule. I was naively thinking that if the Get HTTP Response Action failed to get a response from the server. That it would return a failure to connect notice of some sort to the rule. It does elicit an "Error" response but the failure to connect Error is written to the Hubitat Log whereupon the rule stops processing and no entry is appended to the log file.
I discovered this discussion about monitoring the Hubitat Log file for errors.
https://community.hubitat.com/t/solved-release-how-to-catch-errors-in-log/105353/2
and installed the driver Jost shared [Solved][RELEASE] How to catch errors in log? - #7 by Jost
This did the trick. Thanks Jost and all other supporting characters.
